Heat-treating furnace



Aprill 2, 1929- J. c. wooDsoN4 1,707,294

HEAT TREATING FURNACE Filed Feb. 14, 1928 INVENTOR James C I/aodsa/z.

AT'TORNEY Patented kApr. 2, 1929.

UNiTED sTA'rEs PATENT OFFICE.

JAMES C. WOODSON, 0F MANSFIELD, OHIO, ASSIGNOB, T0 WESTINGHOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA.

HEAT-TREATING FURNACE.

Application led February 14, 1928. Serial No. 254,205.

My invention relates to furnaces and more particularly to electrically heated heattreating furnaces of the pot type.

In furnaces of the above-mentioned type, a crucible is suspended in a 'heating chamber by engagement of the rim'vportion thereof with the side walls of the chamber, an electrical heating element is disposed within the chamber to effect the heating thereof, and a bath comprising 'a fused salt, usually a cyanide, constituting the heating medium is contained in the crucible.

The fused salt, tends to creep, responsive to capillary attraction, over and beyond` the iim of the crucible and over adjacent furnace parts. The action of the fused salt in this respect is similar to that of hot oil, and the creepage-continues until the temperature of the salt is sufficiently reduced to effect the solidification thereof.

The fused salt, particularly in the case of a salt containing cyanide, has a marked deleterious eli'ect upon the outer surface of the crucible, adjacent refractory furnace parts, and the electrical heating element, resulting in the corrosion and subsequent `failure thereof.

It is an object of the present invention,`

therefore, to provide, in a heat-treating furnace, an improved construction whereby the creeping action of the salt beyondfthe rim ofthe crucible and into the furnace chamber is substantially prevented.

In practicing my invention, I provide a crucible operatively supported at the rim portion thereof in a heating chamber, and cooperating means between the crucible rim and supporting structure for preventing the passage of the molten salt therebetween.

In the drawing,

Figure l is a view, in vertical section, of a heat-treating furnace embodying my invention, and

Fig. 2 is an enlarged view, in section of the sealing Ineansl constituting my invention, portions of the furnace and crucible being broken away.

Referring more particularly to the drawing, the furnace embodying my invention comprises a metallic casing 1 and a plurality material, provided with aligned apertures,

are adapted to be maintained in operative superposed relation on the bolts 6. The cooperatlng faces of the blocks 7 are laterally grooved to receive the convolutions of\ an electrical resistance element 8, which is wound in the form of a double helix, coaxial with the axis of the heating chamber.

Since the structure above. described constitutes Ano part of the present invention, a more detailed description thereof is not deemed necessary.

An annular cast-metallic plate 9 is operatlvely supported by engagement with the upper .peripheral edge of the furnace casing 1, and is provided with depending portions 10 adapted to rest upon an annular refractory block 11, constituting a portion of the refractory wall of the furnace. The inner periphery of the plate 9 is provided with an upwardly extending beadmwhich cooperates with a downwardly extending bead formed on the outer periphery of a. second cast metallic plate 12.

The plate 12, as shown more particularly in Fig. 2, is cast to provide a horizontally extending portion 13, adapted to rest upon the refractory block 11, and having, in the upper face thereof, a pair of parallel annular channels 14 and 15 adapted to be filled with a suitable sealing material, as hereinafter described.

A crucible 16 of suitable heat resisting material is provided withv an out-turned rim 17 adapted to cooperate with the inner peripheral ledge of the horizontally extending portion 13 of the plate 12, tosupport the crucible in operative position. As shownmore particularly in Fig. 2, the point of engagement between the crucible rim and the periphery of the portion 13 is such that relative expansion therebetween is permitted.

A suitable heat insulating material 18, such` as asbestos packing, is disposed between the plates 9 and 12 and the refractory block 11, and a suitable heat resistant cement 19 substantially lls the space between the coo erating beads on the lates 9 and 12.

n the under surface o the crucible rim 17 are provided a pair 'of dependingannular Vflanges 20 and 21, -cast integral therewith,

which are adapted to depend into the chan- I nels 14 and 15, respectively.

plate 12. In the channel 15 is disposed a liquid The channel 14 is' substantially filledv with a heat-resistant oement,simila'r to the cement 19, constituting a relatively close oint between the periphery of the rim 'an the which is adapted to chemically react with thefused salt, which may creep therein, to alter the physical and chemical characteristics of said salt, to prevent the further cr 4epage thereof.

t is within the contemplation of my invention to provide a' material inthe channel l15 which will either chemically react with the creeping salt to form a slag, which will not fuse at the operating'temperature of the furnace parts, or to effectively chemil nace a small amount of the fused salt will creep therethrough into the channel 15,' and come in Contact with. the liquid disposed therein.

When a suiiicient .amount of the creeping salt has passed into the channel 15 either to exhaust the supply of material therein or to substantially fill the space between the plates 17 v and 12, any additional salt will tend to flow between the point of support of the crucible rim 17 upon the innerperiphery of the plate 12. When this condition obtains, the crucible must be removed and the materials in the channels 14 and 15 must be renewed.

In .furnaces of the above type. wherein a 4fused salt is employed as the heating medium, the action and the cree ing tl1ereof responsive to capillary attraction, into the heatin chamber will occur even though the nace. The eifect of my construction is tol reduce to ,a minimum, by means of a me- Obviously, many changes may be made l in the structure disclosed, depending upon the requiremehts -of' a particular installation, but it is within the 'scope of my invention to provide a combined mechanical and.

liquid seal so disposed in the path of creeping cyanide that the creeping thereof into the heating chamber is substantially prevented.

Modiications may be made in my invention without departin fromthe spirit and scope thereof, and I esire, therefore, that only such limitations shall be placed thereon as are disclosed b the prior art and imposed by the appen ed claims.

, I claim as my invention:

1. In a heat-treating furnace, the combination with a crucible adapted to contain a fused salt liquid heating medium, of means constituting a combined liquid and mechanical. seal for preventing the creeping of said medium over the outer surface of said crucible. Y

' 2. In a heat-treating furnace, the combi.

adapted to contain a fused salt, ya peripheral rim on said crucible, a support engaging said rim, and cooperating means between said rim and support constituting a combined liquid and mechanical seal for preventing the creeping of said salt therebetween.

4. In a crucible adapted to contain a fused salt, means adjacent the rim of said crucible constituting a liquid seal for preventing the creeping of said salt over the outer surface of said crucible, and means for restricting the amount Aof salt creeping into said liquid seal.

5. In a heat-treating furnace embodying acrucible adapted to contain afused salt, means adjacent to the rim of said crucible constitutin a liquid sealv for preventing creepage o said salt/therethrough, comprising a liquid lof a composition ada ted to chemicallyreact with said'salt to a ter the physical and chemical characteristics thereof, and -means between the rim and the liquid seal for reducing the amount of salt creeping into the liquid seal.

' 6. lIn a heat-treating furnace comprising a crucible adapted ,to contain a'fused liquid T a heating chamber, a plurality of annular channels in said supporting means beneath said crucible rim, annular depending flanges on said rim adapted to cooperate with said channels, means in one of said channels constituting a mechanical seal in the path of `creepage of said liquid, and means in another of said channels for chemically reacting with said creeping liquid to alter the characteristics thereof.

In testimony whereof, I have hereunto 

